Perikinetic aggregation of alkoxylated silica particles in two dimensions

• Aggregation and cluster formation of a two–dimensional colloidal system consisting of 2 mm alkoxylated silica particles trapped at the air-toluene interface has been studied. This novel system allows particle interactions to be controlled by varying the length of the grafted alkyl chains; simple estimates suggest particle bond-strengths of 15 kT and 30 kT for the octadecyl and octyl coated system, respectively. Video enhanced microscopy and image analysis enabled a simultaneously study of kinetics and structure of the ensemble of clusters, in situ. The octyl system displayed a DLCA like structure, Df ≈1.45, while the octadecyl system resulted in a more dense structure, Df ≈ 1.55. The temporal evolution of the cluster-mass distribution displayed a transition point between regimes of slower and faster aggregation for both systems, which was interpreted as a transition from DLCA to convection limited cluster aggregation (CLCA).

Nyckelord

Perikinetic aggregation

particle interactions

fractal dimension

dynamic scaling

image analysis

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